CHAPTER VI 

 WATER 



As oxygen is necessary to the life of plants and animals, so also 

 is water. The human body is saturated with it, and water to 

 make up for evaporation, as well as to aid in digestion, is a most 

 necessary part of our food. The ocean covers about three- 

 fourths of the surface of the earth, and the " dry " land would be 

 uninhabitable if it were really dry. The air always contains more 

 or less water vapor. 



Measurement of the Composition by Weight. An ar- 

 rangement by which the proportion by weight of hydrogen and 



FIG. 31 



oxygen in water can be determined is shown in Fig. 31. The 

 bulb A contains cupric oxide, which is heated. Hydrogen from a 

 generator or cylinder enters on the left and reduces the oxide, 

 forming copper and water: 



Hydrogen + Cupric oxide > Water + Copper. 

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